In case of hydrolysis of a fat or oil by using a lipolytic enzyme, an immobilized enzyme wherein a lipolytic enzyme is immobilized onto an inorganic or organic carrier, is employed for efficient use of the enzyme. The activity of this immobilized enzyme lowers as it is used over time during a hydrolysis reaction, and thus the enzyme must be freshly replaced when its activity reaches a certain low level.
For effective use of the immobilized enzyme recovered after use, one can easily conceive a method of removing from the immobilized enzyme all the oils and proteins adhered thereto and using the carrier again. This method however involves such problems in which it is necessary to wash the waste with liquid amounting to several hundred times as much as the amount of the enzyme carrier and thus is environmentally undesirable, and the activity remaining in the immobilized enzyme after use cannot be completely utilized.
In addition, disclosed are a method of eliminating, from an immobilized lipase whose activity has been lowered after being used for ester exchange or ester transfer reaction, factors obstructive to an enzymatic reaction by washing the enzyme with a solvent (Japanese Patent Application Laid-Open No. 137574/1993); and a method of subjecting lipase, which has lost its water content by the reaction under low moisture conditions, to a wetting treatment with a solvent or a mixture of a solvent and a phospholipid, thereby controlling the water content contributing to the reaction and reactivating the remaining lipase (Japanese Patent Application Laid-Open No. 56379/1997, or Japanese Patent Application Laid-Open No. 75834/1999). The above-described methods however do not regenerate an immobilized enzyme whose activity has been lowered by the loss of part of the lipase, but reactivate the remaining lipase.